The continuous evolution toward electronics with high power densities and integrated circuits with smaller feature sizes and faster speeds places high demands on a set of material properties, namely, the electrical, thermal, and mechanical properties of polymer dielectrics. Herein, a supramolecular approach is described to self-healable polymer nanocomposites that are mechanically robust and capable of restoring simultaneously structural, electrical, dielectric, and thermal transport properties after multiple fractures. With the incorporation of surface-functionalized boron nitride nanosheets, the polymer nanocomposites exhibit many desirable features as dielectric materials such as higher breakdown strength, larger electrical resistivity, improved thermal conductivity, greater mechanical strength, and much stabilized dielectric properties when compared to the pristine polymer. It is found that the recovery condition has remained the same during sequential cycles of cutting and healing, therefore suggesting no aging of the polymer nanocomposites with mechanical breakdown. Moreover, moisture has a minimal effect on the healing and dielectric properties of the polymer nanocomposites, which is in stark contrast to what is typically observed in the hydrogen-bonded supramolecular structures.

The ever-increasing demand for compact electronics and electrical power systems cannot be met with conventional dielectric materials with limited energy densities. Numerous efforts have been made to improve the energy densities of dielectrics by incorporating ceramic additives into polymer matrix. In spite of increased permittivities, thus-fabricated polymer nanocomposites typically suffer from significantly decreased breakdown strengths, which preclude a substantial gain in energy density. Herein, organic–inorganic hybrids as a new class of dielectric materials are described, which are prepared from the covalent incorporation of tantalum species into ferroelectric polymers via in situ sol-gel condensation. The solution-processed hybrid with the optimal composition exhibits a Weibull breakdown strength of 505 MV m⁻¹ and a discharged energy density of 18 J cm⁻³, which are more than 40% and 180%, respectively, greater than the pristine ferroelectric polymer. The superior performance is mainly ascribed to the deep traps created in the hybrids at the molecular level, which results in reduced electric conduction and lower remnant polarization. Simultaneously, the formation of the cross-linked networks enhances the mechanical strengths of the hybrid films and thus hinders the occurrence of the electromechanical breakdown. This work opens up new opportunities to solution-processed organic materials with high energy densities for capacitive electrical energy storage.

The coupling of the magnetic, electric, and elastic properties in multiferroics creates new collective phenomena and enables next-generation device paradigms. In this work, the hydrogen bonding interaction between hydrate salts and ferroelectric polymers is exploited in the development of high-performance magnetoelectric (ME) polymer laminate composites. The microstructures and crystallite structures of the Al(NO₃)₃·9H₂O doped poly(vinylidene fluoride-co-hexafluoropropylene), P(VDF-HFP), are carefully studied. The effect of hydrogen bonding interaction on the polarization ordering of the ferroelectric polymers is investigated by 2D wide-angle X-ray diffraction, polarized Fourier transform infrared spectra, and dielectric spectra at varied frequencies and temperatures. It is found that hydrogen bond not only promotes the formation of the polar crystallite phase but also improves the polarization ordering in the ferroelectric polymer, which subsequently increases the remnant polarization of the polymers as verified in the polarization-electric field loop measurements. These entail marked improvement in the ME voltage coefficients (α_ME) of the resulting polymer laminate composites based on ferromagnetic Metglas relative to analogous composites. The composite exhibits a state-of-the-art α_ME value of 20 V cm^-1 Oe under a dc magnetic field of ≈4 Oe and a colossal α_ME of 320 V cm^-1 Oe at a frequency of 68 kHz.

This review highlights the frontier scientific research in the development of polymer nanocomposites for electrical energy storage applications. Considerable progress has been made over the past several years in the enhancement of the energy densities of the polymer nanocomposites via tuning the chemical structures of ceramic fillers and polymer matrix and engineering the polymer–ceramic interfaces. This article summarizes a range of current approaches to dielectric polymer nanocomposites, including the ferroelectric polymer matrix, increase of the dielectric permittivity using high-permittivity ceramic fillers and conductive dopants, preparation of uniform composite films based on surface-functionalized fillers, and utilization of the interfacial coupling effect. Primary attentions have been paid to the dielectric properties at different electric fields and their correlation with film morphology, chemical structure, and filler concentration. This article concludes with a discussion of scientific issues that remain to be addressed as well as recommendations for future research. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1421–1429, 2011

New classes of fluorinated polymer–polysilsesquioxane nanocomposites have been designed and synthesized. The synthesis method includes radical polymerization using the functional benzoyl peroxide initiator for the telechelic fluorinated polymers with perfluorosulfonic acids in the side chains and a subsequent in situ sol–gel condensation of the prepared triethoxylsilane-terminated fluorinated polymers with oxide precursors. The telechelic polymer and nanocomposites have been carefully characterized by ¹H and ¹⁹F NMR, FTIR, TGA, and TEM. The ion-exchange capacity (IEC), water uptake, the state of the absorbed water, and transport properties of the composite membranes have been extensively studied as a function of the content and structure of the fillers. Unlike the conventional Nafion/silica composites, the proton conductivity of the prepared membranes increases steadily with the addition of small amounts of the polysilsesquioxane fillers. In particular, the sulfopropylated polysilsesquioxane-based nanocomposites display proton conductivities greater than Nafion. This is attributed to the presence of pendant sulfonic acids in the fillers, which increases IEC and offers continuous proton transport channels between the fillers and the polymer matrix. The methanol permeability of the prepared membranes has also been examined. Lower methanol permeability and higher electrochemical selectivity than those of Nafion have been demonstrated in the polysilsesquioxane-based nanocomposites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010

A series of ferroelectric poly(vinylidene fluoride-trifluoroethylene- chlorotrifluoroethylene), P(VDF-TrFE-CTFE), have been synthesized by a two-step approach. The first step is copolymerization of VDF and CTFE via solution or suspension methods to produce P(VDF-CTFE) copolymers with different molecular weights. The second step is partial de-chlorination to convert copolymers into P(VDF-TrFE-CTFE) terpolymers with precisely controlled compositions. The effect of molecular weight, molecular weight distribution and uniaxially stretching on the dielectric properties has been investigated over a broad range of temperature and frequency. The X-ray diffraction patterns and DSC curves demonstrate the coexistence of the multiple phases in the terpolymers. The dielectric spectra depict the local relaxation processes and relaxor ferroelectric behavior on the basis of the dielectric loss tangent as a function of temperature.